The hefty new penalties under New Zealand's gun law changes

Gun owners will have until the end of September to hand in any illegal firearms - including those soon to be banned by the Government - and if not, they'll face hefty new penalties.

Parliament will urgently debate gun laws on Tuesday as the Government makes good on its promise to introduce legislation banning the firearms used in the March 15 Christchurch massacre.

The new legislation includes up to two years imprisonment for selling or possessing a prohibited part, up to five for possessing a prohibited gun, and up to seven years for pointing a prohibited gun at someone.

The changes will happen quickly, with the proposed law signed off by Cabinet on Monday which goes to Parliament on Tuesday, giving people a week to submit. By the end of next week, a law will be in place.

Police told Newshub that since 3pm on the day of the March 15 Christchurch shooting, there have been 211 firearms voluntarily handed in to police.

Details of a buy-back scheme are yet to be announced, but one thing is for certain: if you bought it after the Government announced a ban, tough luck.

Police Minister Stuart Nash said on Monday that anyone who purchased one of the soon-to-be banned firearms after the Government's announcement is "foolish".

"If you were foolish enough to buy after the Order in Council had come into force, then you would not be compensated for it," he said during a post-Cabinet press conference.

Analysis of official police figures by Newshub show that over the 10-year period from 2008 to 2017, there were 76 murders or manslaughters with a firearm, with seven committed by someone who held a gun licence.

This is just the first set of gun law changes to get in front of Parliament.

Deputy Prime Minister Winston Peters expects the next steps - including a look at online sales, and any potential register of guns - by the end of the year.